arXiv subjects
Publications and source records attributed to Daniel Gómez Dumm.
We analyse Belle data on the decay $τ^- \to π^- π^0 ν_τ$ using a dispersive representation of the vector form factor which is consistent with chiral symmetry and preserves analyticity and unitarity exactly. We fit the unknown theoretical parameters from the data, determining the values of the related low-energy observables $\left\langle r^2\right\rangle^π_V$ and $c_V^π$. The implementation of isospin breaking effects is also discussed.
The hadronization structure of $τ^- \to ηπ^- π^0 ν_τ$ decays is analyzed using Chiral Perturbation Theory with resonances, considering only the contribution of the lightest meson resonances at leading order in the $1/N_C$ expansion. After imposing the asymptotic behavior of vector spectral functions ruled by QCD, unknown effective couplings are determined by fitting the $τ^- \to ηπ^- π^0 ν_τ$ branching ratio and decay spectrum to recent data. Predictions for the partner decay $τ^- \to η^\prime π^- π^0 ν_τ$ and the low-energy behavior of the cross section $σ(e^+e^-\to ηπ^+π^-)$ are also discussed.